1. Field of the Invention
The present invention relates to methods for installing a guide path for an automatic guided vehicle system, and in particular to a method for installing such a guide path having an inductive loop disposed beneath a wood block floor.
2. Description of the Prior Art
Automatic vehicle guidance systems, so-called "driverless" systems, are known which utilize an inductive loop embedded in the floor of the facility in which the system is to be used. The loop in some instances may be taped to the floor of the facility. The inductive loop provides a predetermined route which vehicles will follow as they travel throughout the facility to perform a variety of functions. The guide paths must be accurately located relative to the floor plans and may include information points, intersections, bypasses, station stops and other features which may be integrated in the system design. Conventional guidance networks generally include signal wiring connected to pilot line drivers which, when energized, may generate up to five different frequencies which serve as signals which are detected by sensors disposed on the vehicles. Simpler systems may be utilized having only one signal frequency.
The latout for such vehicle guidance systems may range from simple to very complex depending upon the requirements of the customer. Most systems are in the category of complex systems wherein several load or unload positions, several vehicles, several information points, and integration with other systems are required. The guide path thus also becomes an information network permitting the vehicles and a control computer to communicate with each other via the network sensors and information points. It is essential that all of the systems interfaces within the guide path are installed properly to have an effective trouble-free operating system.
The vehicles utilized in such systems vary in size, capacity and functions. The vehicles also vary in the manner of design and placement of the drive and steering wheels of the vehicle, causing a variety of guide path conditions to be encountered. When two different types of vehicles must operate in the same system, it will be necessary to have two guide paths which may overlap and operate at different signal frequencies. These conditions will affect the turning radii of the vehicles, the entering or leaving of a transaction station by a vehicle, and locations of the sensors with respect to the guide path. Much of this detail may be included by the engineering group providing the system equipment, however, the installer or installation crew must be knowledgeable with respect to the overall system parameters for incorporating the desired functions into the actual floor plan.
The generally accepted conventional method of installing signal wire or guide wire by imbedding the wire in the floor is as follows. A floor plan is first laid out according to the design detials for metting the user's requirements. Floor slots are cut, normally in a concrete floor to the depth and width specified including curves, turns and bypasses according to the previously made floor layout. The signal wires are placed in the floor slots according to the wiring diagram and are tested for continuity. The floor slots are backfilled with one of several commercially available concrete grouting compounds which are poured or troweled or gunned into the slots. The material when applied is usually wet and is forced into the slots by some means so as to completely surround the wires in the slots. The grouting material is then troweled so as to be even with the floor surface, and is permitted to cure for a period of three to four hours. Care must be taken to apply the grouting product in a manner which allows for a certain degree of shrinkage during curing, and material must be added or removed as required in order to achieve a finished installation which is flush with the floor surface. The objective is to achieve a smooth surface with no depressions or voids, and no raised or rounded areas, on the guide path or along the return cuts.
A similar procedure is followed for installing a guide path for an automatic guided vehicle system in a wood block floor. Wood block floors are generally constructed of approximately 4 inch by 6 inch wooden blocks, with a nominal thickness of 21/4 inches parallel with the grain. The blocks are treated with Creosote and are normally installed over a sub-floor of concrete using pitch as an adhesive to hold the blocks in place. In some instances a coating of pitch may be used on the surface of the block floor. Due to the construction and composition of such wood block floors, the floors tend to move or shift due to humidity, other moisture, equipment traffic, and other forces encountered on a day-to-day basis. Because of such movement, conventional methods of installing guide paths for guided vehicle systems in facilities having wood block floors require removal of the wood blocks in a path of sufficient width to accommodate the vehicle along the complete length of the guide path. Light weight concrete is substituted for the removed blocks and the concrete path is then cut and wired as described above. The foregoing is a very expensive process and for that reason is seldom used.
Whether installed in a floor consisting completely of concrete or in a concrete path within a wood block floor, conventional installation methods for automatic vehicle system guide paths result in the guide path wires essentially becoming an integral part of the floor, once the grout is fully cured. The grout material in conventional installation methods hardens almost as hard as the surrounding concrete. Concrete floors, like wood block floors, are subject to expansion, contraction, settling and other deterioration over a period of time. Moreover, in industrial plants where machinery is in operation, other forces such as vibration, shock loading, heavy load carrying vehicles, and the like will be encountered which adds stresses or strains to the guide path areas. These forces and external disruptions make the embedded signal wires subject to breakage or separation which requires repairs to be made and interruption of the system during such repairs. Such repair of conventional installations requires extreme care and hand chiseling in order to gain access to the embedded wires once the trouble area is identified. This is a difficult and time consuming process. The same procedure is necessary if the system is to be expanded or changed in the future.